What does HTTP 502 mean?
A gateway or proxy received an invalid response from the upstream server.
Common causes and when you see it
The application server crashed, restarted or is unreachable from the reverse proxy.
How to fix or handle it
Check that the upstream (PHP-FPM, Node, etc.) is running and the proxy points at the right address and port.
Test it yourself
Send a request with the online API tester, inspect the response with the HTTP header checker, or host an endpoint that returns 502 with the mock API generator to see how your app reacts.
Server errors hurt users and SEO. Monitor your endpoints so you know about 502 responses before your customers do.
HTTP 502 questions
A gateway or proxy received an invalid response from the upstream server.
The application server crashed, restarted or is unreachable from the reverse proxy.
Check that the upstream (PHP-FPM, Node, etc.) is running and the proxy points at the right address and port.